The Government is being called on to do all it can to stop the new EU-South American trade deal going through.
The Irish Farmers Association says the Mercosur deal is bad for farming communities, the environment and the consumer.
The agreement will see 99,000 tonnes of beef enter EU markets.
It now needs to be approved by the European Parliament, European Council and member states before being rubber stamped.
IFA President Joe Healy says farmers are outraged and disappointed, particularly with Brexit on the horizon:
"Even with the UK in Europe we are already over 102% self-sufficient in beef," said IFA President Joe Healy
"If the UK leaves on a no-deal, the EU looks likely to be 116% self-sufficient
"That is a million tonnes of surplus beef on the European market.
"99,000 tonnes extra coming in from the Mercosur countries will increase that by 10%," he added.